Did you follow the instructions in the error to install the Cineware plug-in?
On the After Effects page in the Creative Cloud Desktop app, click the overflow menu (three dots) and choose "Add-ons," then see if Cineware is already installed. See the attached screenshots.
Gotcha, in that case I moved this conversation to the Bugs section. If you have anymore information, please add it here to give the AE team the best chance of reproducing the issue.